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Subject: Problem installing PyEpics
From: Alan Kastengren <akastengren@anl.gov>
To: <tech-talk@aps.anl.gov>
Date: Mon, 30 Jan 2017 09:59:40 -0600
I am trying to get a development machine on Linux RHEL 7 configured so I can work on PyEpics scripting, and I am having some difficulties. I have installed EPICS base 3.14.12.6 and set the PYEPICS_LIBCA, EPICS_BASE, and EPICS_HOST_ARCH environment variables. I'm using the Anaconda Python distribution (version 2.7 of Python) on a local install on my machine (since it's a laptop and won't always have access to APSshare). I installed PyEpics through conda (version 3.2.6), as described on the PyEpics website for installation instructions. I can perform caput and caget from the Bash shell, so I believe EPICS itself is working correctly. My problem is that if start an interactive Python session I can import epics and perform caput and caget, instantiate a PV object, etc just fine. If I try to run the exact same commands from a script, I can still import epics without an error, but I get the error shown below whenever I first try to do either a caget or instantiate a PV object. I've confirmed that the runtime is looking in the same location for the library file in both the interactive session and the script, and that both have the same sys.path (except for the local directory being on the path for the scripted version) and Python version. I'm really at a loss.

Traceback (most recent call last):
File "/home/akastengren/anaconda2/lib/python2.7/site-packages/epics/ca.py", line 215, in initialize_libca
    libca = load_dll(dllname)
File "/home/akastengren/anaconda2/lib/python2.7/ctypes/__init__.py", line 440, in LoadLibrary
    return self._dlltype(name)
File "/home/akastengren/anaconda2/lib/python2.7/ctypes/__init__.py", line 362, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: /home/akastengren/anaconda2/bin/../lib/libreadline.so.6: undefined symbol: PC
Traceback (most recent call last):
File "/home/akastengren/Python/workspace/PyEpics_Scripting/Test_install.py", line 9, in <module>
    print(epics.caget('7bmb1:m1.VAL'))
File "/home/akastengren/anaconda2/lib/python2.7/site-packages/epics/__init__.py", line 81, in caget
    thispv = get_pv(pvname, connect=True)
File "/home/akastengren/anaconda2/lib/python2.7/site-packages/epics/pv.py", line 39, in get_pv
    context = ca.current_context()
File "/home/akastengren/anaconda2/lib/python2.7/site-packages/epics/ca.py", line 362, in wrapper
    initialize_libca()
File "/home/akastengren/anaconda2/lib/python2.7/site-packages/epics/ca.py", line 217, in initialize_libca raise ChannelAccessException('loading Epics CA DLL failed: ' + str(exc)) epics.ca.ChannelAccessException: loading Epics CA DLL failed: /home/akastengren/anaconda2/bin/../lib/libreadline.so.6: undefined symbol: PC
Replies:
Re: Problem installing PyEpics Pete Jemian
Re: Problem installing PyEpics Vodopivec, Klemen

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